The present invention relates to a core, a rotating electric machine using the core and used for driving a fun, disc, or the like, and a production method of the core.
The current of arts relating to a stator structure of inner rotation type motor is that in order to improve an occupation ratio of winding to an area, a core is divided each pole and the divided cores are fastened each other by laser beam welding, or press-fitted and shrinkage-fitted in a cylindrical housing positioned at the periphery of the core.
On the other hand, in a stator of an outer rotation type motor, magnetic tooth portions (teeth) are formed in an annular shape at the outer periphery of rib-shaped core portion extending in a radial direction from an inner core portion formed in an annular shape and a magnetic gap between the stator and a magnetic rotor is formed at the outer peripheral portion of the core, so that it is difficult to fasten core portions to each other at the outer peripheral portion of the core and it is impossible to effect press fit and shrinkage fit of a member such as a cylindrical housing from the peripheral portion of the core.
Here, consideration is given to a case where a core division production method which is taken for conventional inner rotation type motors is applied for outer rotation type motors. That is, considering the shrinkage fit in reverse, it is considered that a housing is arranged at an inner peripheral portion of a core and gives stress to the core side. This means expansion fit, that is, the housing which is chilled by such means as liquid nitrogen to be lower than a room temperature is arranged at an inner peripheral portion of the core, and the housing expands when the temperature returns to the room temperature and gives stress to the core. However, even if the stress is give outwardly to peripherally divided cores, the divided cores only expand in a radial direction and can not be fastened each other.
For such reasons, it was difficult for outer rotation type motor stators and winding type direct current motor rotors to employ a core division production method of dividing a core and assembling the divided cores to form the complete core.
Prior arts relating to a structure that a stator core of outer rotation type motor is divided are disclosed in JP A 10-94230 and JP A 11-252844, for instance. In the stator construction according to the prior arts, a stator core is divided into a yoke portion and teeth portions, both of which have dove tail structures, and the divided cores are assembled each other by fitting the dove tail structures each other. In each of the core division production methods according to the prior arts, fastening of the yoke portion and teeth portions is done only by press fit, so that the fastened core is weak in mechanical strength as a product. Therefore, considering that teeth tips receive reaction force of torque when the core is used as a motor, the methods can not be used for motors of large torque.
Further, JP A 7-203644 discloses a similar prior art to the above prior arts. This prior art does not relate to a stator in which a winding is wound, but relates to a rotor construction of inner rotation type, which is composed of magnetic pieces having a dovetail shape for holding a magnetic disposed inside the rotor and a support portion of non-magnetic material. In the construction, also, the core components are fastened to be a core by simple press fit and any adherent is not used, which is disclosed in the document. The construction can not be applied to a motor of high rotation and high torque because centrifugal force is applied to the magnet.
Still further, another conventional method using connection core is disclosed in JP A 2000-152528. In this method, core pieces which were punched in a linear shape with tips of teeth thereof connected finely to each other, are subjected to winding and then assembled in a circular core shape after completion of the winding. Finally it is necessary to fix one portion of an end portion by any means. In this example, a method of fixing it by using continuous pins is disclosed, it also can be fixed by welding or the like. However, in this method, since magnetic materials are connected between magnetic poles, magnetic flux s leak between the magnetic poles, and the efficiency of the motor is remarkably reduced. Further, since the width of the connecting portion can not be made sufficiently wide for a mechanical reason, mechanical strength lacks and it is not sufficient for a high torque motor.
An object of the present invention is to provide, in an electric rotating machine having a core which has an annular inner core portion, a rib-shaped core portion extending radially form the annular inner core portion and an outer peripheral core portion that magnetic pole tooth portions are formed in an annular shape on the outer periphery of the rib-shaped core portion, a core which is formed by assembling core blocks, for example, each divided each pole for raising an occupation ratio of winding per an area, which core has mechanical strength equivalent to that of a core made of segments each of which is punched out in a complete core shape.
The above-mentioned object is achieved by a core which has an annular inner core portion, a rib-shaped core portion extending radially form the annular inner core portion and an outer peripheral core portion that magnetic pole tooth portions are formed in an annular shape on the outer periphery of the rib-shaped core portion, wherein the core is composed of a plurality of core blocks having the same shapes as blocks formed by dividing the core in circumferential direction, the plurality of core blocks each having a concave/convex engage portion at an inner peripheral portion corresponding to the inner periphery of the annular inner core portion, and the plurality of core blocks gathered so as to form the core are fastened each other by a cylindrical housing having an outer surface formed in concave/convex shape, inserted in the inner peripheral portion so as to engage with each other at the concave/convex engage portions, and changed in diameter relative to the core blocks due to thermal shrinkage or expansion of the cylindrical housing, whereby the core blocks are tightly fitted to each other without any gap between adjacent core blocks.